TW201320106A - Paste and method for connecting electronic component to substrate - Google Patents

Abstract

The invention provides a paste that can be used to connect at least one electronic component to at least one substrate through contact regions, whereby at least one of said contact regions contains a non-noble metal. Said paste contains (a) metal particles, (b) at least one activator that bears at least two carboxylic acid units in the molecule, and (c) a dispersion medium.

Description

Paste and method for connecting electronic components to a substrate

The present invention relates to a paste for connecting an electronic component to a substrate and a method of connecting the electronic component to the substrate.

In the field of power electronics, fastening electronic components to a substrate is a particular problem.

The mechanical stress generated during operation of the terminal device requires that the connection between the electronic component and the substrate be of sufficient strength to prevent the electronic component from separating from the substrate. Therefore, a lead-containing solder paste is usually used, which produces a connection layer which exhibits high reliability in terms of strength in a soldering process. Because lead is toxic and related to health hazards, it is looking for suitable alternatives to these lead-containing solder pastes. It is currently discussed that as an alternative to lead solder, lead-free solder pastes are well suited for creating high strength tie layers between electronic components and substrates. However, such solders have a low melting point that is slightly higher than the temperature at which the electronic components are exposed during operation. Therefore, the strength reliability of the connection layers is significantly reduced during operation of the electronic components.

The high reliability of the connection strength between the electronic component and the substrate can be achieved using a variety of bonding agents and connection methods. However, such conditions typically require high process temperatures and high process pressures that result in damage to the parts to be joined and high defect rates in high volume production.

This is a potential cause of reducing the process temperature and process pressure required for such joining methods. Therefore, adhesives are used to join the parts in some applications. By using an adhesive, connecting electronic components can be obtained in some cases A high strength bonding layer to the substrate. However, a disadvantage of the adhesion technique is that the thermal conductivity and conductivity of the resulting contact point between the electronic component and the substrate are generally insufficient.

In order to meet the requirements for the reliability, thermal conductivity and electrical conductivity of the connection points, it has been proposed for a period of time to connect the electronic components to the substrate via sintering (see, for example, DE 10 2007 046 901 A1). Sintering technology is a very simple way to connect components in a stable manner. Using such sintering methods, electronic components are often connected to the substrate quite successfully, with the proviso that they each contain a contact zone containing a precious metal. However, it is often desirable to connect the electronic component to the substrate via at least one non-noble metal contact region. It is generally not feasible to create a stable connection via such non-noble metal contact regions using conventional sintering methods.

Furthermore, it has been proposed earlier to use a paste based on nanoparticle particles having a particle diameter of not more than 100 nm to connect the electronic component to the substrate. However, the handling of nanoparticles is associated with health hazards and is therefore often avoided by occupational safety.

Accordingly, it is an object of the present invention to provide a paste that connects at least one electronic component to at least one substrate via a contact zone, wherein at least one of the contact zones contains a non-noble metal. Preferably, the paste is applied to form a connection between the electronic component and the substrate that ensures high reliability at the temperature at which the electronic component is exposed during operation. Moreover, the paste preferably also overcomes other disadvantages known from the prior art.

It is also an object of the present invention to provide a method of joining at least one electronic component to at least one substrate via a contact zone, wherein at least one of the contact regions contains a non-noble metal.

These objectives are achieved by the subject matter of the independent item.

Accordingly, the present invention provides a paste comprising (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersion medium.

Moreover, the present invention provides a method of connecting at least one electronic component to at least one substrate via a contact region, wherein at least one of the contact regions contains a non-noble metal, the method comprising the steps of: (i) providing a first contact region a substrate and an electronic component having a second contact region, wherein at least one of the contact regions contains a non-noble metal; (ii) a paste comprising (a) metal particles; (b) at least one in the molecule An activator having at least two carboxylic acid units; and (c) a dispersion medium; (iii) a structure in which the first contact region of the substrate contacts the second contact region of the electronic component via the paste; And (iv) sintering the structure while producing a module comprising at least a substrate and an electronic component interconnected via a sintered paste.

The invention is based on the absolutely surprising insight that it is possible, by means of sintering, to connect an electronic component to a substrate via at least one contact zone comprising a non-noble metal, which is heretofore impossible, with the proviso that the paste is contained in the molecule An activator with at least two carboxylic acid units.

According to the present invention, a paste is provided.

The definition of the term paste is not limited. However, the paste is better understood as meaning Any dispersion that can be applied via common coating techniques, such as printing techniques (such as screen printing or stencil printing), dispersion techniques, spray techniques, stitch transfer or dipping, and having a sufficiently high viscosity and cohesion to allow subsequent The step processes the applied paste.

The paste of the present invention contains (a) metal particles.

Metal particles are preferably understood to mean particles containing metals.

According to a preferred embodiment, the metal is selected from the group consisting of copper, silver, nickel and aluminum. According to a particularly preferred embodiment, the metal is silver.

The metal may be present in the metal particles as a pure metal, for example having a purity of at least 99% by weight, a purity of at least 99.9% by weight, a purity of at least 99.99% by weight or a purity of at least 99.999% by weight. On the other hand, the metal particles may also contain a plurality of metals. It is also possible that the metal particles contain an alloy composed of a plurality of metals or an intermetallic phase.

According to a preferred embodiment, the metal particles comprise as an essential component an element selected from the group consisting of silver, copper, nickel and aluminum. Within the scope of the present invention, a principal component is understood to mean an element that is present in a metal particle of interest that is greater than any other element present in the metal particle.

According to a particularly preferred embodiment, the metal particles are silver particles, copper particles, nickel particles or aluminum particles. The surface of the particles may be partially or fully oxidized, as appropriate.

According to a particularly preferred embodiment, the metal particles are silver particles.

The shape of the metal particles is not limited. Preferably, the metal particles are in the shape of a sheet, an ellipsoid or a circle. It is also possible that the metal particles are a mixture of various shapes.

According to a particularly preferred embodiment, the metal particles are in the shape of a sheet. In this embodiment, the fraction of the flakes is at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight, and particularly preferably at least 99% by weight, based on the total weight of the metal particles. .

According to another preferred embodiment, the metal particles have a length ratio greater than 1.0, a better length ratio greater than 1.2, even more preferably a length ratio greater than 1.5, and particularly preferably a length ratio greater than 2.0. Preferably, the metal particles have a length ratio of not more than 20, a better length ratio of not more than 15, and even more preferably a length ratio of not more than 10. In this context, the length ratio is understood to mean the distance (a) extending the widest part of the cross section of the metal particles and the widest point of the cross section extending along a line perpendicular to the distance (a). The ratio of distance (b). In this case, the cross section is a section that passes through the metal particles and has the largest surface area. If the metal particles have, for example, a rectangular cross section, the length ratio is the ratio of the length to the width of the cross section. For example, a metal particle having a rectangular cross section having a length of 2 μm and a width of 1 μm has a length ratio of 2.

According to another preferred embodiment, the fraction of metal particles having a length ratio greater than 1.0, the fraction of metal particles having a better length ratio greater than 1.2, and even the fraction of metal particles having a length ratio greater than 1.5 are at least 70% by weight. More preferably, it is at least 80% by weight, and even more preferably at least 90% by weight, each based on the total weight of the metal particles.

The metal particles present in the paste may have different particle size distributions.

According to a preferred embodiment, the metal particles have an average particle diameter (d50 value) of at least 500 nm, more preferably at least 650 nm, and even more preferably at least 1 μm. The average particle diameter (d50 value) is preferably not more than 20 μm, more preferably not more than 15 μm, And even better, no more than 10 μm. Therefore, the average particle diameter (d50 value) is preferably in the range of 500 nm to 20 μm, more preferably in the range of 650 nm to 15 μm, and even more preferably in the range of 1 to 10 μm. Preferably, the average particle diameter (d50 value) is understood to mean a particle diameter in which 50% by volume of the metal particles are not reached and 50% by volume of the metal particles exceed.

According to another preferred embodiment, the metal particles have a particle diameter d10 (d10 value) of at least 150 nm, more preferably at least 200 nm, and even more preferably at least 250 nm. The particle diameter d10 (d10 value) is preferably not more than 5 μm, more preferably not more than 4 μm, and even more preferably not more than 3 μm. Therefore, the particle diameter d10 (d10 value) is preferably in the range of 150 nm to 5 μm, more preferably in the range of 200 nm to 4 μm, and even more preferably in the range of 250 nm to 3 μm. Preferably, the particle diameter d10 (d10 value) is understood to mean a particle diameter in which 10% by volume of the metal particles do not reach and 90% by volume of the metal particles exceed.

According to another preferred embodiment, the metal particles have a particle size d90 (d90 value) of at least 1.75 μm, more preferably at least 2 μm, and even more preferably at least 2.25 μm. The particle diameter d90 (d90 value) is preferably not more than 100 μm, more preferably not more than 50 μm, and even more preferably not more than 25 μm. Therefore, the particle diameter d90 (d90 value) is preferably in the range of 1.75 μm to 100 μm, more preferably in the range of 2 μm to 50 μm, and even more preferably in the range of 2.25 μm to 25 μm. Preferably, the particle diameter d90 (d90 value) is understood to mean a particle diameter in which 90% by volume of the metal particles are not reached and 10% by volume of the metal particles exceed.

Analysis of the particle size to a particle size suitable for the ISO 13320 (2009) determined via the LALLS (low angle laser light scattering (Low Angle Laser Light Scattering)) method. In this context, preferably, Mastersizer 2000 (Malvern Instruments Ltd., Worcestershire, United Kingdom) is used as a measuring instrument. The measurement and the analysis are carried out under suitable conditions (for example: standard: silver with a refractive index of 0.14, absorbance of 3.99; dispersion medium: ethanol with a refractive index of 1.36; procedure: adding 200 ml of ethanol to 0.5 g of powder) The resulting suspension was sonicated for 5 minutes, and then an aliquot of the suspension for measurement was transferred to a Hydro Accessory of Mastersizer 2000 ; an optical model for analysis: Mie theory.

Preferably, the specific surface area of the metal particles is in the range of from 1 m ² /g to 5 m ² /g and more preferably from 1 m ² /g to 4 m ² / according to BET ( Brunauer , Emett , Teller ). Within the scope of g. Preferably, this BET measurement is carried out in accordance with DIN ISO 9277:2003-05.

Metal particles may also be present as a mixture of metal particles of various fractions, as appropriate. The aliquot may vary, for example, depending on the composition, shape or size of the metal particles.

Preferably, the metal particles have a fraction of at least 50% by weight, more preferably at least 60% by weight, even more preferably at least 70% by weight, and particularly preferably at least 80% by weight, based on the total weight of the paste. . Preferably, the fraction of the metal particles is not more than 95% by weight, more preferably not more than 93% by weight, and even more preferably not more than 90% by weight, based on the total weight of the paste. Therefore, the fraction of the metal particles [preferably] is in the range of 50% by weight to 95% by weight, more preferably in the range of 60% by weight to 93% by weight, and even more preferably, based on the total weight of the paste. It is in the range of 70% by weight to 90% by weight.

The metal particles can comprise a coating.

Within the scope of the invention, the coating of metal particles is understood to mean a firm adhesive layer on the surface of the metal particles. Preferably, a firm adhesive layer means that the layer does not separate from the metal particles only by gravity.

The coating of metal particles often contains at least one coating compound.

The at least one coating compound is preferably an organic compound.

Preferably, the coating compound is selected from the group consisting of saturated compounds, monounsaturated compounds, polyunsaturated compounds, and mixtures thereof.

Preferably, the coating compound is selected from the group consisting of branched chain compounds, unbranched compounds, and mixtures thereof.

Preferably, the coating compound has from 8 to 28, even more preferably from 12 to 24 and especially preferably from 12 to 18 carbon atoms.

According to a preferred embodiment, the coating compound is selected from the group consisting of fatty acids, fatty acid salts and fatty acid esters.

Conceivable fatty acid salts are preferably those wherein the anionic component is a deprotonated fatty acid and the cationic component thereof is selected from the group consisting of ammonium ions, monoalkylammonium ions, dialkylammonium ions, trialkylammonium ions, lithium. A group consisting of ions, sodium ions, potassium ions, copper ions, and aluminum ions.

Preferred fatty acid esters are derived from the corresponding fatty acids in which the hydroxyl group of the carboxylic acid unit is replaced by an alkyl group, especially a methyl, ethyl, propyl or butyl group.

According to a preferred embodiment, the at least one coating compound is selected from the group consisting of caprylic acid/octanoic acid, capric acid/decanoic acid, lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), mixtures thereof, and corresponding esters and salts, and mixtures thereof.

According to a particularly preferred embodiment, the at least one coating compound is selected from the group consisting of lauric acid (dodecanoic acid), stearic acid (octadecanoic acid), sodium stearate, potassium stearate, aluminum stearate, stearic acid A group consisting of copper acid, sodium palmitate and potassium palmitate.

The coated metal particles used are preferably commercially available. The corresponding coating compound can be applied to the surface of the metal particles by techniques commonly used in the art.

By way of example, the coating compound, in particular the stearate or palmitate mentioned above, can be slurried in a solvent and the slurried coating compound wet-milled together with the metal particles in a ball mill. After the wet grinding, the metal particles coated with the coating compound are dried until then, and then the dust is removed.

Preferably, the fraction of at least one coating compound selected from the group consisting of fatty acids, fatty acid salts and fatty acid esters is at least 80% by weight, more preferably at least 90% by weight, based on the total weight of the coating, especially It is preferably at least 95% by weight, even more preferably at least 99% by weight, and especially 100% by weight.

According to a preferred embodiment, the total fraction of the coating compound is from 0.05 to 3% by weight, more preferably from 0.07 to 2.5% by weight, and even more preferably from 0.1 to 2.2, based on the total weight of the coated metal particles. weight%.

The degree of coating defined as the ratio of the mass of the coating compound to the surface area of the metal particles is preferably from 0.00005 to 0.03 g, more preferably from 0.0001 to 0.02 g, and even more preferably 0.0005 per square meter (m ² ) of metal particle surface area. 0.02 g of coating compound.

Surprisingly found that coatings on metal particles significantly improve electronic components Reliability of the connection strength with the substrate.

According to the invention, the paste also contains at least one activator (b).

The activator carries at least two carboxylic acid units in the molecule. Accordingly, the activator may also carry more than two, more than three or more than four carboxylic acid units in the molecule.

The position of the carboxylic acid unit in the molecule is not limited. However, the carboxylic acid unit of the activator is preferably saturated at the terminal position.

Furthermore, the carboxylic acid unit of the activator is via no more than five carbon atoms, more preferably no more than four carbon atoms, even more preferably no more than three carbon atoms, particularly preferably no more than two carbon atoms and even more particularly no more than It has proven to be advantageous to interconnect one carbon atom. Further, it is preferred that the carboxylic acid units of the activator are linked to each other via at least one carbon atom. The number of carbon atoms used for determining the interconnection of the carboxylic acid units of the activator and the number of carbon atoms of the carboxylic acid unit itself should not be included in the calculation according to the scope of the present invention. Thus, for example, in the case of malonic acid (HOOCCH ₂ COOH), the carboxylic acid units are linked to each other via one carbon atom, and in the case of maleic acid (HOOC(CH) ₂ COOH), the carboxylic acid The units are connected to each other via two carbon atoms.

According to a preferred embodiment, the activator comprises at least 2 carbon atoms and more preferably at least 3 carbon atoms. Preferably, the activator comprises no more than 18 carbon atoms, more preferably no more than 14 carbon atoms, even more preferably no more than 12 carbon atoms, especially preferably no more than 10 carbon atoms, even more preferably no more than 8 carbon atoms, and especially no more than 6 carbon atoms. Therefore, the activator preferably contains 2 to 18 carbon atoms, more preferably 2 to 14 carbon atoms, even more preferably 2 to 12 carbon atoms, particularly preferably 2 to 10 carbon atoms, more preferably For 2-8 One carbon atom, especially 2-6 carbon atoms or 3-6 carbon atoms.

The activator can be a saturated or unsaturated compound.

The unsaturated activator preferably comprises at least one carbon-carbon bond in the molecule. Furthermore, the cis isomer has proven to be a particularly advantageous activator.

The activator can be a branched or unbranched compound.

The length, type and position of the side chain of the branched chain activator are not subject to any restrictions. Preferably, the branched chain activator comprises at least one side chain having a length of from 1 to 8 carbon atoms. Typically, the side chain is an alkyl chain which may be substituted as appropriate.

The activator can be an aromatic or aliphatic compound. However, the activator is preferably an aliphatic compound.

The activator of the present invention may carry other heteroatoms in addition to the oxygen atoms present in the carboxylic acid unit. However, the activator preferably does not contain a hetero atom other than the oxygen atom in the carboxylic acid unit.

Preferably, the carboxylic acid unit of the activator is present in the paste in an aprotonated form. Therefore, it may be advantageous to select a dispersion medium suitable for dissociating the carboxylic acid unit.

In many cases it has proven to be advantageous for the decomposition point of the activator to be below 300 ° C, more preferably below 270 ° C, even more preferably below 240 ° C and especially preferably below 200 ° C. In such cases, the decomposition point of the activator is preferably in the range of from 100 ° C to 300 ° C, more preferably in the range of from 110 ° C to 270 ° C, even more preferably in the range of from 120 ° C to 240 ° C, and especially It is preferably in the range of 130 ° C to 200 ° C.

Furthermore, it has proven to be advantageous in many cases for the activator to have a melting point of at least 80 ° C, more preferably at least 90 ° C and even more preferably at least 100 ° C. here In other cases, the melting point is preferably not more than 200 ° C, more preferably not more than 180 ° C, and even more preferably not more than 160 ° C. Therefore, the melting point of the activator is preferably in the range of 80 ° C to 200 ° C, more preferably in the range of 90 ° C to 180 ° C, and even more preferably in the range of 100 ° C to 160 ° C.

The activator can be presented in a non-composite form. Alternatively, the activator may be present in a composite form, preferably in the form of a complex comprising a subgroup element of the periodic system of elements. If the activator is present in a complex form, it may especially be a complex dicarboxylic acid.

According to a preferred embodiment, the activator is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid (cis-butenedioic acid/ Maleic acid), trans-butenedioc acid/fumaric acid, cis-2-pentenoic acid, trans-2-pentenoic acid and dimethylmalonic acid.

According to a particularly preferred embodiment, the activator is selected from the group consisting of oxalic acid, malonic acid, maleic acid and dimethylmalonic acid.

According to an even more particularly preferred embodiment, the activator is selected from the group consisting of oxalic acid, malonic acid, maleic acid and dimethylmalonic acid.

The fraction of the activator is preferably at least 0.1% by weight, more preferably at least 0.3% by weight, even more preferably at least 0.5% by weight, particularly preferably at least 1% by weight, based on the total weight of the paste, and even More particularly preferably it is at least 2% by weight. Preferably, the fraction of activator is not more than 30% by weight, more preferably not more than 20% by weight, even more preferably not more than 10% by weight, particularly preferably not more than 7% by weight, based on the total weight of the paste. And even more preferably it is not more than 5% by weight. Correspondingly, the fraction of activator is based on the total weight of the paste. In the range of 0.1% by weight to 30% by weight, more preferably in the range of 0.3% by weight to 20% by weight, even more preferably in the range of 0.5% by weight to 10% by weight, particularly preferably 1% by weight to 7% by weight Within the range of %, and even more particularly preferably in the range of 2% by weight to 5% by weight.

Further, the paste of the present invention contains a dispersion medium (c).

It is preferred that the metal particles (a) are dispersible in the dispersion medium (c). At least one activator (b) may also be dispersed in the dispersion medium (c). However, it is also possible that the activator (b) is dissolved in the dispersion medium (c).

Dispersion media can be a dispersion medium that is common in the art.

Thus, the dispersion medium can contain one or more solvents.

In this context, organic compounds are, for example, conceivable solvents.

The organic compounds preferably have 5 to 50 carbon atoms, more preferably 8 to 32 carbon atoms, and even more preferably 18 to 32 carbon atoms.

The organic compound may be a branched or unbranched compound. The organic compound may also be a cyclic compound.

The organic compound may also have aliphatic or aromatic properties.

Further, the organic compound used as a solvent may be a saturated or monounsaturated or polyunsaturated compound.

The organic compound may also contain a hetero atom, especially an oxygen atom or a nitrogen atom. The heteroatoms can be part of a functional group. Functional groups conceivable include, for example, a carboxylic acid group, an ester group, a ketone group, an aldehyde group, a hydroxyl group, an amine group, a decylamino group, an azo group, a quinone imine group, a cyano group or a nitrile group.

Therefore, as a solvent, for example, α-terpineol ((R)-(+)-α-terpineol, (S)-(-)-α-terpineol or racemate), β - terpineol, gamma-terpineol, Δ-terpineol, a mixture of the aforementioned terpineols, N-methyl-2-pyrrolidone, ethylene glycol, dimethylacetamide, alcohols (especially containing not having 5-9 carbon atoms) Branches or branched chains of their alcohols), 1-hexanol, 1-octanol, 1-dodecyl alcohol, 1-tridecanol, 2-tridecanol, 3-tridecanol, 4-tridecyl alcohol , 5-tridecyl alcohol, 6-tridecyl alcohol, isotridecyl alcohol, dibasic ester (preferably dimethyl glutarate, adipic acid or dimethyl succinate or a mixture thereof), glycerin, diethylene Alcohol, triethylene glycol or a mixture thereof.

According to another preferred embodiment, the dispersion medium contains at least one aprotic solvent. It may also be advantageous for the fraction of at least one aprotic solvent to be at least 70% by weight, based on the total weight of all components of the paste which is liquid at a temperature of 25 ° C and a pressure of 1.1013 bar, more preferably At least 80% by weight, even more preferably at least 90% by weight, particularly preferably at least 95% by weight, and even more preferably at least 99% by weight.

The aprotic solvent is preferably selected from the group consisting of aliphatic hydrocarbon compounds, carboxylic acid esters, and ethers.

According to a particularly preferred embodiment, the dispersion medium contains at least one aliphatic hydrocarbon compound. The aliphatic hydrocarbon compound preferably contains 5 to 50 carbon atoms, more preferably 8 to 32 carbon atoms, and even more preferably 18 to 32 carbon atoms.

Therefore, the aliphatic hydrocarbon compound may also be paraffin wax.

The fraction of the dispersion medium is preferably at least 5% by weight, more preferably at least 8% by weight, and even more preferably at least 10% by weight, based on the total weight of the paste. The fraction of the dispersion medium is preferably not more than 40% by weight, more preferably not more than 30% by weight, even more preferably not more than 20% by weight, and particularly preferably not more than 15% by weight, based on the total weight of the paste. Correspondingly, the total weight of the paste The fraction of the dispersion medium is preferably in the range of from 5% by weight to 40% by weight, more preferably in the range of from 8% by weight to 30% by weight, and even more preferably in the range of from 10% by weight to 20% by weight. .

When appropriate, the paste of the present invention may contain other materials than the metal particles (a), at least one activator (b), and the dispersion medium (c).

Other substances which are conceivable are thinners, thickeners and stabilizers which are common in the art.

Preferably, the fraction of (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersing medium is preferably not based on the total weight of the paste. More than 20% by weight, more preferably not more than 15% by weight, even more preferably not more than 10% by weight, particularly preferably not more than 5% by weight, even more preferably not more than 3% by weight, and especially not more than 1% by weight.

The paste of the present invention can be produced by methods common in the art.

The paste can be produced, for example, by mixing metal particles (a), at least one activator (b) having two carboxylic acid units in the molecule, and a dispersion medium (c).

According to a particularly preferred embodiment, the paste is produced in a plurality of steps.

In this context, at least one activator (b) is wet milled in a first step. Wet milling can be carried out in a mill and used to improve the dispersibility of the activator in the dispersion medium (c).

The wet-milled activator (b) can then be combined with the dispersion medium (c) in a second step. A homogeneous suspension of activator (b) in dispersion medium (c) is typically produced in this step. To produce the homogeneous suspension, the mixture can be treated with a mixer (e.g., an Ultraturax mixer) as appropriate.

Finally, the suspension from the second step can be combined with the metal particles (a) in the third step. Merged in the middle. Subsequently, the resulting mixture is homogenized as appropriate, for example by hand. The mixture can then be passed through a roller mill and further homogenized as needed. The resulting paste can then be used for the intended purpose.

The paste of the present invention is preferably used to connect at least one electronic component to at least one substrate.

In this process, at least one of the electronic components is preferably fastened to the substrate.

This fastening is achieved via sintering. Within the scope of the invention, sintering is understood to mean the joining of two or more components via heating without the production of a liquid phase. Therefore, sintering preferably results in a firmly bonded connection between the at least one electronic component and the substrate.

As is well known in the art, electronic components are understood to be articles that can be part of an electronic device. According to a preferred embodiment, an electronic component is understood to mean a single component that cannot be further disassembled and that can be used as a component of an electronic circuit. As a unit, the electronic component may be composed of a plurality of components as appropriate. The electronic component can be, for example, an active component or a passive component. According to a particular embodiment, the electronic components are used in high power electronic instruments. Preferably, the electronic component is selected from the group consisting of lines consisting of: diode (e.g., LED (light emitting diode (light emitting diode)), transistors (e.g. IGBT (insulated gate bipolar transistor (insulated-gate bipolar transistor ), that is, bipolar transistors with insulated gate electrodes, integrated circuits, semiconductor wafers, bare wafers ( die ), resistors, sensors, capacitors, coils, and heat sinks.

Generally, a substrate is understood to mean an object that can be attached to an electronic component. According to a preferred embodiment, the substrate is selected from the group consisting of a lead frame , a DCB substrate ( direct copper bonded substrate), and a ceramic substrate.

According to a preferred embodiment, the following pairs of electronic components and substrates are interconnected: LED/ lead frame , LED/ceramic substrate, die / lead frame , die /ceramic substrate, die /DCB substrate, diode/ lead Frame , diode/ceramic substrate, diode/DCB substrate, IGBT/ lead frame , IGBT/ceramic substrate, IGBT/DCB substrate, integrated circuit/ lead frame , integrated circuit/ceramic substrate, integrated circuit/DCB Substrate, sensor/ lead frame , sensor/ceramic substrate, heat sink (preferably copper or aluminum heat sink) / DCB, heat sink (preferably copper or aluminum heat sink) / ceramic substrate, heat sink / Lead frame , capacitor (preferably tantalum capacitor, more preferably tantalum capacitor in open state) / lead frame .

According to another preferred embodiment, a plurality of electronic components can be coupled to the substrate. Further, it is preferable to dispose the electronic component on the opposite side of the substrate.

However, both the electronic component and the substrate comprise at least one contact zone.

Within the scope of the present invention, a contact zone is understood to mean the area of an electronic component that contacts the electronic component via the paste of the invention in the area or substrate in contact with the substrate via the paste of the invention. Accordingly, the contact area of the electronic component preferably includes a contact surface that is covered by the substrate once the substrate is attached thereto. Likewise, the contact area of the substrate preferably includes a contact surface that is covered by the electronic component once the electronic component is attached thereto. Preferably, the volume of the contact area of the electronic component is defined by the contact surface of the contact area of the electronic component (defined by the width and length of the contact surface) and a thickness of 50 nm. Similarly, the volume of the contact area of the substrate is preferably defined by the contact surface of the contact area of the substrate (defined by the width and length of the contact surface) and a thickness of 50 nm. The volume of the contact area of the electronic component and the substrate has a specific weight. The weight can be, for example, by means of Oujie Auger spectroscopy is determined by removing the contact area by sputtering and then measuring the weight of the removed area.

The contact area can be an area that is applied to an electronic component or substrate. For example, in many cases, metallization is applied to the surface of the electronic component to be connected. This metallization can, in many cases, occupy a thickness in the range of 100 nm to 400 nm. Metallization of this type or a region thereof can represent the contact zone of the present invention.

Alternatively, the contact area can be an integrated component of an electronic component or substrate. For example, according to the present invention, a lead frame made of copper can be used as the substrate. The thickness of the lead frames can be in the range of a few millimeters. In this case, the other areas of the lead frame in the material or structure does not have to different regions of the lead frame may represent a contact zone of the present invention.

At least one of the contact regions of the electronic component and the substrate contains at least one non-noble metal.

According to a preferred embodiment, at least one of the electronic component and the substrate comprising the non-noble metal contact region contains at least one element selected from the group consisting of: (i) copper, aluminum, zinc, and nickel; (ii) includes at least one selected An alloy of elements of copper, aluminum, zinc, and nickel; and (iii) an intermetallic phase comprising at least one element selected from the group consisting of copper, aluminum, zinc, and nickel.

The fraction of at least one non-noble metal (e.g., a non-noble metal selected from the group consisting of copper, aluminum, zinc, and nickel) is preferably at least 5% by weight, more preferably at least 7 by weight, based on the weight of the contact zone comprising the non-noble metal. %, even more preferably at least 10% by weight, particularly preferably at least 15% by weight, even more preferably at least 50% by weight, and especially at least 90% by weight.

Preferably, the non-noble metal (more preferably selected from the group consisting of copper, aluminum, zinc and nickel) is the main component of the contact zone. Within the scope of the invention, the principal component of the contact zone is understood to mean an element which is present in the contact zone and which is greater than any other element present in the contact zone.

Within the scope of the invention, the contact zone comprising non-noble metals may also comprise other elements, including in particular noble metals.

If the contact zone comprising a non-noble metal contains an alloy comprising at least one element selected from the group consisting of copper, aluminum, zinc and nickel, the alloy may be, for example, an alloy consisting essentially of copper, nickel, zinc and common impurities or substantially consisting of tin An alloy of gold and common impurities.

In a first step of the method of the present invention, a substrate having a first contact region and an electronic component having a second contact region are provided, wherein at least one of the contact regions contains a non-noble metal.

Therefore, the contact area of the substrate, the contact area of the electronic component or the contact area of the substrate and the contact area of the electronic component may contain a non-precious metal.

By definition, the substrate comprises a first contact zone and the electronic component comprises a second contact zone. Further, the substrate or electronic component can include other contact areas as appropriate. For example, if a leadframe is used as a substrate, the leadframe typically contains a plurality of (adjacent) contact regions to be connected to a plurality of electronic components to form a secondary assembly.

In the next step of the process of the invention, a paste according to the definition provided above is provided.

Accordingly, the paste contains (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersion medium.

A structure is created in another step of the method of the invention.

The structure contains at least a substrate, an electronic component, and a paste. In this context, the paste is located between the first contact area of the substrate and the second contact area of the electronic component. Thus, the first surface of the substrate contacts the second surface of the electronic component by means of a paste.

The structure can be produced, for example, by applying a paste to the contact surface of the first contact region of the substrate and placing the electronic component on the applied paste by the contact surface of the second contact region. Also, the structure can be produced, for example, by applying a paste to the contact surface of the second contact region of the electronic component and placing the substrate on the applied paste by the contact surface of the first contact region. The coating paste can preferably be carried out by means of coating techniques commonly found in the art, for example by means of printing methods such as screen printing or stencil printing, dispersion techniques, spray techniques, stitch transfer or dipping.

The distance between the first surface of the substrate and the second surface of the electronic component (measured after the structure is formed, that is, substantially according to the thickness of the paste) is preferably in the range of 20 μm to 200 μm, and more preferably 50 Between μm and 100 μm.

Once the structure is created, it can be dried (if appropriate). Preferably, the structure is dried at a temperature in the range of from 80 ° C to 200 ° C and more preferably in the range of from 100 ° C to 150 ° C. Drying is preferably carried out for a period of from 2 to 20 minutes, and more preferably from 5 to 10 minutes. If desired, the drying may be carried out instead or additionally under and preferably under the conditions mentioned above, while producing a structure, for example, prior to placing the electronic component on the paste applied to the substrate or placing the substrate thereon. Before being applied to the paste on the electronic component.

In a further step of the method of the invention, the structure comprising the substrate, the electronic component and the paste is sintered.

After sintering, the metal particles present in the paste are baked together with at least a portion of the contact zone. The remaining components present in the paste are typically removed from the paste during this process, such as by evaporation after undergoing chemical conversion, as appropriate. Sintering is carried out based on a diffusion process in which elements present in the metal particles of the paste diffuse into the contact zone and the elements present in the contact zone diffuse into the space formed between the metal particles of the paste. Since the temperature and diffusion rate in this process dominate, a stable and firm bond is formed.

Preferably, the sintering of the structure is effected by heating to a temperature of at least 150 ° C, more preferably at least 175 ° C and even more preferably at least 200 ° C. Preferably, the sintering of the structure is achieved by heating to a temperature of no greater than 350 ° C and even more preferably no greater than 300 ° C. Therefore, it is preferred to heat the structure to a temperature in the range of 150 ° C to 350 ° C, more preferably in the range of 150 ° C to 300 ° C, even more preferably in the range of 175 ° C to 300 ° C, and especially It is preferably a temperature in the range of 200 ° C to 300 ° C.

The heating is preferably carried out without applying any process pressure, that is, at a process pressure of 0 kbar, but can also be carried out under a high process pressure, for example, at a process pressure of 1 kilobar or more. .

Heating is preferably carried out for a period of from 1 to 60 minutes, and more preferably from 2 to 4 minutes.

There is no limit to the atmosphere in which heating can be achieved. However, the heating is preferably carried out in an atmosphere containing oxygen.

Sintering is carried out in a conventional apparatus of the art suitable for sintering and preferably setting the above process parameters.

After sintering, a module is obtained that contains at least a substrate and electronic components interconnected via a sintered paste.

According to a particularly preferred embodiment, the method of the invention for connecting at least one electronic component to at least one substrate is performed via a contact zone, wherein at least one of the contact zones contains copper as a non-noble metal. The use of a paste containing (a) metal particles, (b) at least one compound selected from the group consisting of malonic acid, maleic acid and oxalic acid as an activator and (c) a dispersion medium has been demonstrated in this case. It is especially beneficial.

According to another particularly preferred embodiment, the method of the invention for joining at least one electronic component to at least one substrate is performed via a contact zone, wherein at least one of the contact zones contains nickel as a non-noble metal. It has proven to be particularly advantageous in this case to use a paste comprising (a) metal particles, (b) at least one compound selected from the group consisting of dimethylmalonic acid and oxalic acid as the activator and (c) a dispersion medium. .

The invention is illustrated below by examples, which do not limit the scope of the invention.

Example:

The pastes 1-3 of the present invention and the reference pastes 1-3 were prepared according to the compositions of Table 1 below as follows:

In six different samples (for pastes 1-3 and reference pastes 1-3), the corresponding activator is first wet-milled in a coffee mill followed by addition to the dispersion medium. These mixtures were allowed to produce a homogeneous suspension using an Ultraturax mixer. The homogeneous suspension is then added to the silver powder. The resulting mixture was first manually homogenized using a spatula, then passed through a roller mill three times and homogenized again to obtain paste 1-3 and reference paste 1-3.

The lead frame is attached to the semiconductor wafer using paste 1-3 and reference paste 1-3.

Lead frames made of copper or nickel and silver metallized semiconductor wafers are used for this purpose.

Paste 1-3 and reference paste 1-3 were applied to the respective lead frames in the six samples. The semiconductor wafer is then placed on the applied paste. The distance between the surface of the semiconductor wafer opposite to the lead frame is of 80 μm. The structure thus obtained was pre-dried at a temperature of 150 ° C for 5 minutes. Subsequently, the structure thus obtained was sintered at a temperature of 250 ° C under no pressure.

After the sintering process, an analysis is performed to evaluate the existence of the connection between the semiconductor wafer and the lead frame and the reliability of the connection.

The results of this analysis are summarized in Table 2.

These tests show that a stable connection is formed using only the pastes 1-3 of the present invention, but a stable connection is not formed when the reference pastes 1-3 are used.

Claims (10)

A paste comprising (a) metal particles; (b) at least one activator having at least two carboxylic acid units in the molecule; and (c) a dispersion medium. The paste of claim 1, wherein the metal particles are silver particles. A paste according to claim 1 or 2, wherein the activator has a decomposition point in the range of from 100 °C to 300 °C. The paste of any one of claims 1 to 3, wherein the activator is selected from the group consisting of dicarboxylic acids and complex dicarboxylic acids. The paste of any one of claims 1 to 4, wherein the activator is selected from the group consisting of malonic acid, maleic acid, dimethylmalonic acid, and oxalic acid. The paste of any one of claims 1 to 5, wherein the dispersion medium contains an aliphatic hydrocarbon compound. A method of connecting at least one electronic component to at least one substrate via a contact region, wherein at least one of the contact regions contains a non-noble metal, the method comprising the steps of: (i) providing a substrate having a first contact region and having a An electronic component of two contact regions, wherein at least one of the contact regions contains a non-noble metal; (ii) providing a paste comprising (a) metal particles; (b) at least one activator having at least two carboxylic acid units in the molecule; and (c) a dispersion medium; (iii) generating a structure, wherein the first contact region of the substrate contacts the paste via the paste The second contact region of the electronic component; and (iv) sintering the structure while producing a module comprising at least the substrate and the electronic component interconnected via the sintered paste. The method of claim 7, wherein at least one of the contact areas is an integrated component of the electronic component or the substrate. The method of claim 7 or 8, wherein the non-noble metal is copper and the activator is selected from the group consisting of malonic acid, maleic acid, and oxalic acid. The method of claim 7 or 8, wherein the non-noble metal is nickel and the activator is selected from the group consisting of dimethylmalonic acid and oxalic acid.